Without delay, here is my unnecessarily detailed and long post on how to do this thoroughly without breaking anything.
It is airbag equipped models that have horn buttons, so start by disconnecting the battery because we don't want airbags blowing up in our faces. You should wait over a minute to make sure the backup capacitor for the airbags is discharged as well.
There are four bolts holding the airbag/horn button assembly onto the steering wheel, two on each side.
The two covers can be pried off easily, I use my fingers.
The bolts require a Torx T-30 bit to unscrew. If you're weird like me you can buy one at your local auto-parts store then return it when you're done, so long as you didn't destroy the packaging (I'm like a surgeon).
Removed the large yellow airbag connector first because the wires are shorter, then the white horn connector. To unlock the airbag connector, press down on the top of the connector on the right side just to the right of the green part hooking into it. The green button should then pop out on the left side of the connector.
Bonus question: what's the only visible modification I've made to my Legacy here?
To removed the horn buttons remove the screw from the metal plate and pull the red wire's connector off carefully with some needle nosed pliers.
Next push out the horn button assembly. This is best done by pushing on the edge of the trim colored plastic through the center hole where the screw was. It takes a lot of force for something so simple, that's why it's best to push in the middle so that you don't bend it one way or another.
If there's nothing to get a hold of in the middle you can try here.
The resulting horn button assembly. Notice part of the plastic broken off at the top, that was from me trying to pry the button itself out earlier. I actually spent 15 minute trying to find that tiny plastic piece to glue it back on.
Carefully remove the outer button from its casing by pushing in as many tabs as you can. A helpful friend may aid. Again you can see the piece I broke off from trying to pry the button out while it was in the steering wheel...
Look at that CRAP. I don't even know what it is. Maybe the previous owner spilled coffee on the steering wheel somehow.
Look for defects in the plastic like this and scraped them flat with an exacto knife or something similar.
Also do the same for deformations you might have caused prying the button out, but if you did it right you shouldn't have pried it out.
When reinstalling the airbag/horn assembly after plugging in the yellow airbag connector you MUST push in the green button on the left of the airbag connector before reconnecting battery or the airbag will NOT be enabled and the airbag light on the dash will always be on. In this picture the green button has not yet been pushed in.
Bonus question answer: The gauge needles have been painted red with a Sharpie marker.
